import React, {useEffect, useRef} from "react";
import _ from 'lodash'
import './background_bulestar.less'

const BackgroundBuleStar = () => {
    const canvasRef = useRef(null);
    const canvasRef2 = useRef(null);

    useEffect(() => {
        initBg(canvasRef.current);
    }, [])

    function initBg(canvas) {
        let ctx = canvas.getContext('2d');
        let w = canvas.width = document.body.clientWidth;
        let h = canvas.height = document.body.clientHeight;

        let hue = 217;
        let stars = [];
        let count = 0;
        let maxStars = 500;//星星数量

        let canvas2 = document.createElement('canvas');
        let ctx2 = canvas2.getContext('2d');
        canvas2.width = 100;
        canvas2.height = 100;
        let half = canvas2.width / 2;
        let gradient2 = ctx2.createRadialGradient(half, half, 0, half, half, half);
        gradient2.addColorStop(0.025, '#CCC');
        gradient2.addColorStop(0.1, 'hsl(' + hue + ', 61%, 33%)');
        gradient2.addColorStop(0.25, 'hsl(' + hue + ', 64%, 6%)');
        gradient2.addColorStop(1, 'transparent');

        ctx2.fillStyle = gradient2;
        ctx2.beginPath();
        ctx2.arc(half, half, half, 0, Math.PI * 2);
        ctx2.fill();

// End cache

        const random = (min, max) => {
            let maxTemp;
            let minTemp;
            if (arguments.length < 2) {
                maxTemp = min;
                minTemp = 0;
            }

            if (min > max) {
                maxTemp = min;
                minTemp = max;
            }

            return Math.floor(Math.random() * (maxTemp - minTemp + 1)) + minTemp;
        }

        function maxOrbit(x, y) {
            let max = Math.max(x, y),
                diameter = Math.round(Math.sqrt(max * max + max * max));
            return diameter / 2;
            //星星移动范围，值越大范围越小，
        }

        let Star = function () {

            this.orbitRadius = random(maxOrbit(w, h));
            this.radius = random(60, this.orbitRadius) / 2;
            //星星大小
            this.orbitX = w / 2;
            this.orbitY = h / 2;
            this.timePassed = random(0, maxStars);
            this.speed = random(this.orbitRadius) / 200000;
            //星星移动速度
            this.alpha = random(2, 10) / 10;

            count++;
            stars[count] = this;
        }

        Star.prototype.draw = function () {
            let x = Math.sin(this.timePassed) * this.orbitRadius + this.orbitX,
                y = Math.cos(this.timePassed) * this.orbitRadius + this.orbitY,
                twinkle = random(10);

            if (twinkle === 1 && this.alpha > 0) {
                this.alpha -= 0.05;
            } else if (twinkle === 2 && this.alpha < 1) {
                this.alpha += 0.05;
            }

            ctx.globalAlpha = this.alpha;
            ctx.drawImage(canvas2, x - this.radius / 2, y - this.radius / 2, this.radius, this.radius);
            this.timePassed += this.speed;
        }

        for (let i = 0; i < maxStars; i++) {
            new Star();
        }

        function animation() {
            ctx.globalCompositeOperation = 'source-over';
            ctx.globalAlpha = 0.5; //尾巴
            ctx.fillStyle = 'hsla(' + hue + ', 64%, 6%, 2)';
            ctx.fillRect(0, 0, w, h)

            ctx.globalCompositeOperation = 'lighter';
            for (let i = 1, l = stars.length; i < l; i++) {
                stars[i].draw();
            }

            window.requestAnimationFrame(animation);
        }

        animation();
    }

    return (

        <canvas id='canvas' className='canvas' ref={canvasRef}></canvas>

    )
}
export default BackgroundBuleStar